Some warmth is normal. A granny charger, its plug and the socket will feel warm during a long charge, because a domestic socket is carrying close to its continuous limit for hours. What is not normal is heat you cannot comfortably keep your hand on, a hot or discoloured socket, a buzzing sound, or a smell of hot plastic or fish — stop charging and have the socket and plug checked before you use them again.
Key Takeaways
- Warm is normal after hours of charging; too hot to touch, marks or smells are not.
- Heat concentrates at worn sockets and loose plugs, and at coiled cable.
- Never use an extension lead or adapter with a granny charger.
- For daily use, a dedicated circuit fitted by a qualified electrician is the cooler option.
Why Granny Charging Makes Heat
Heat rises with current and with resistance. A granny charger typically draws about 10 A in the UK for many hours at a time. Any extra resistance — a worn socket contact, a loose plug pin, a dirty terminal — turns into heat at that point, and heat makes contacts worse, which makes more heat. The control box on the cable gets warm for a different reason: its electronics are working and sealed against water, so it sheds heat through the casing. Our guide to whether EV charging cables get hot explains the same physics for charging cables generally.
Warm vs Too Hot: What to Check
| Sign | Usually normal | Stop and get it checked |
|---|---|---|
| Control box | Warm to the touch | Too hot to hold, deformed casing |
| Plug and socket | Slightly warm after hours | Hot, brown marks, cracked or loose socket |
| Cable | Neutral, fully uncoiled | Warm while still coiled on a reel or in a loop |
| Sound and smell | Silent, no smell | Buzzing, crackling, hot-plastic or fishy smell |
Two habits cause avoidable heat. Charging with the cable still coiled traps warmth in the loop, so uncoil it fully. And never run a granny charger through an ordinary extension lead: our portable EV charger safety guide and the advisory on extension cords explain why leads overheat and are not a workaround.
How to Keep Socket Charging Cool
- Plug directly into the wall socket — no extension lead, no multi-way adapter.
- Uncoil the whole cable before you start, every time.
- Use a socket in good condition; replace one that is loose, cracked or already discoloured.
- Feel the plug and socket after the first hour of a long charge; warmth is expected, heat is not.
- Keep the control box out of standing water and direct heat, and let air reach it.
The long-term answer is a dedicated charge point on its own circuit, installed by a qualified electrician. A socket circuit was designed for varied household loads, not for one heavy load running all night, which is why guidance such as the IET Code of Practice treats granny charging as occasional use.
A Cooler Way to Charge at Home
If you rely on a granny charger every day, a portable unit with adjustable current lets you trade speed for a gentler load. The EVDANCE EV-ACS3210E 32A Type 2 portable charger covers up to about 7 kW single-phase on a proper circuit, and at socket-level use its settings let an installer or experienced user keep current sensible for the supply. For daily charging, ask a qualified electrician about a dedicated circuit instead of pushing a household socket harder.
Frequently Asked Questions
Is it normal for the plug to be warm after charging overnight?
Mild warmth is common after hours at about 10 A. Heat you cannot hold your hand against, marks on the socket, or any smell is not normal — stop and have the socket replaced or checked.
Why does the socket get hotter than the cable?
Because the contact points are where resistance concentrates. A worn socket grips the plug pins loosely, and that poor contact is exactly where heat builds first.
Can I keep using a granny charger that gets hot?
No. Heat is an early warning, not a quirk. Stop using that socket, do not move the problem to an extension lead, and get a qualified electrician to inspect the circuit.
Related Reading
- Do EV Charging Cables Get Hot?
- Portable EV Charger Safety Guide 2026
- Can I Charge an Electric Car From a Normal Socket?
- Does a Level 1 Charger Need a Dedicated Circuit?
